The problem is not going to be issuing a visa. The problem is likely to be at the immigration check point when entering Thailand who can see your travel records. By all means try and get a new passport and go that way but I’m just stating most people these days have a problem when entering the country rather than getting the actual visa.
If this is your first report they will give you a form to fill in when you arrive if it’s a repeat visit in the Jomtien Office they staple in a blue notification of stay into your passport and you exchange this for a new notification at counter 4 I think it is.
Immigration records are kept on a computer database so having a new passport is irrelevant. They can still see your travel history in and out of Thailand.
No such thing as a 9 month ED visa, how long you can stay depends on many variables but normally you will be staying on an extension of stay and not the visa itself. I know many people who entered on a ED visa studying to become divemaster.
Every consulate in England, Scotland, Wales and Ireland have to obtain authorisation from the London Embassy to issue that particular visa. As Tod mentioned, better to just go direct to London and I would be surprised if you get the ME I’m pretty sure they will only give the 90 days from what I have heard